New "expanded carrier screening" tests allow us to screen donors for hundreds of genetic mutations. Should we?
One of the upsides of the pandemic is that events that used to be off limits due to distance are now available via Zoom. The Progress Educational Trust (PET), a UK-based non-profit, has been hosting fascinating programs for years, but I've never been able to attend one. The other week, I finally made it.
Sure, it was the day after Labour Day, and I was driving home along a remote stretch of northern Ontario's Highway 17, and I could only connect by cell phone — but I was there! For most of it, anyway, until my coverage cut out right near the end.
Their title says it all: "Careful What You Look For: What Should We Be Testing For in Sperm and Egg Donors?"
The reason we're interested in testing donors at all, of course, is that each donor provides half the genes that will create the child. A person carries two versions ("alleles") of each gene, one from each parent, but only one will be expressed. That is the dominant version. The recessive version stays silent. The donor could pass either version to the child.
Sometimes our recessive versions have a disease-causing mutation, but we are unaware of it. If both biological parents have that same disease-causing version, the child could inherit two copies. Two copies could condemn the child to developing the disease. Cystic fibrosis, Tay-Sachs and sickle cell anemia are all examples of diseases passed on through recessive mutations.
In the old days, we screened for a small number of conditions, one by one. Now, however, "expanded carrier screening" makes it possible to test for hundreds of conditions all at once. Most people have never even heard of the majority of these conditions — things like Bloom syndrome, Canavan disease, and Carbamoyl phosphate synthetase I deficiency — let alone realized they were carrying mutations for them.
You can see why intended parents would want to screen donors as thoroughly as possible. But what about the donors themselves — what's right for them?
Guido Pennings, director of the Bioethics Institute Ghent, in Belgium, argues that the interests of the donors are being ignored. He spoke in the meeting and also published a piece in advance of it. Below, I summarize some of the important points he raises.
Intended parents are not required to undergo expanded carrier screening, even though they have an even larger moral obligation toward the child to prevent disease than the donor does.
Expanded carrier screening, despite all the conditions it tests for, only reduces risk of harm by about one percent. Other things that could reduce risk of harm to a child by at least one per cent include giving up smoking, following a strict diet, having the child at a younger age — and these interventions are not required either.
In some countries, two high-quality embryos can be transferred at one time, resulting in twins. "The very small risk reduction obtained by [expanded carrier screening] is largely undone by the increase in morbidity and mortality due to multiple pregnancies."
A donor isn't necessarily interested in learning more about their genes.
The results of genetic testing may have implications for the donor's own health.
The results of the genetic testing may have implications for the donor's future reproductive choices.
Many people decide not to do genetic testing, and it's widely agreed people should have that freedom. IVF patients, intended parents, and the general population are among those who routinely turn it down. Donors are often denied this choice. "This is strange, since donors may have exactly the same psychological, social and ethical objections against obtaining genetic information as other people do: not wanting to know, anxiety, threat to privacy, and discrimination."
We need to think more about how to manage the information gained through expanded carrier screening of donors. Who is the rightful recipient of this information? How should the information be shared?
What happens to a donor's genetic privacy now that anonymity is mostly a thing of the past?
What happens to a donor's genetic privacy when the donor is a friend or family member?
Payment complicates matters. Payment may make it feel that the interests of the donor don't count as much as the interests of the intended parents — but they do.
Watch the meeting: "Careful What You Look For: What Should We Be Testing For in Sperm and Egg Donors?
Guido Pennings. "Expanded carrier screening: ignoring the interests of gamete donors?" BioNews. 2020.
Marieke Bigg. "Expanded carrier screening: careful what you look for." BioNews. 2020.
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